The present invention relates to separators for oil and gas wells, and more particularly to a rotary, downhole, gas and liquid separator and a downhole method of separating gas and liquid from production fluid.
Liquids are substantially incompressible fluids while gases are compressible fluids. The production fluid in an oil or gas well is generally a combination of liquids and gases. In particular, the production fluid for methane production from coal formation includes the gas and water. Pumping such production fluid is difficult due to the compressibility of the gas. Compression of the gas reduces the efficiency of the pump and the pump can cavitate, stopping fluid flow. Downhole gas and liquid separators separate the gas and liquid in the production fluid at the bottom of the production string, before pumping the liquid up the production string, and thereby improve the efficiency and reliability of the pumping process. In some cases, the waste fluids from the production fluid may be reinjected above or below the production formation, eliminating the cost of bringing such waste fluids to the surface and the cost of disposal or recycling.
U.S. Pat. No. 5,673,752 to Scudder et al. discloses a separator that uses a hydrophobic membrane for separation. U.S. Pat. No. 6,036,749 to Ribeiro et al., U.S. Pat. No. 6,066,193 to Lee and U.S. Pat. No. 6,382,317 to Cobb disclose powered rotary separators. U.S. Pat. No. 6,155,345 to Lee et al. discloses a separator divided by flow-through bearings into multiple separation chambers.
A downhole separator includes a housing defining an interior cavity, a means for restricting fluid flow, an internal pump and a vortex generator. The means for restricting fluid flow is located in the housing and divides the interior cavity into a first chamber and a second chamber. The internal pump pumps production fluid into the first chamber and through the means for restricting flow. The means for restricting flow generates a pressure drop in production fluid entering the second chamber, causing the gas and liquid to separate. The vortex generator segregates the liquid to the outside and gas to the inside of the second chamber. The method of separating liquid and gas from production fluid includes pumping production fluid into a first chamber, generating a pressure drop in the production fluid as the production fluid flows from the first chamber into a second chamber, and generating a vortex in the production fluid in the second chamber.